Dicyanoisophorone-based fluorescent probe for detecting H₂S and monitoring nitroprusside metabolism

Hydrogen sulfide (H₂S) is an important multifunctional gasotransmitter that plays a pivotal role in regulating various physiological processes. Recent studies have shown that sodium nitroprusside (SNP), a commonly used drug for treating hypertension and angiectasis, will produce H₂S during its metabolism. Thus, real-time monitoring of H₂S can track the metabolic processes of SNP in vivo. In this study, we designed and synthesized a novel near-infrared (NIR) fluorescent probe, RM, based on the mechanism of excited-state intramolecular proton transfer (ESIPT). The probe features dicyanoisophorone as the fluorophore and a 2,4-dinitrobenzene structure as the recognition group for H₂S detection. Upon reaction with H₂S, RM exhibited a 11.6-fold fluorescence enhancement at 688 nm, with a detection limit of 0.83 μM, demonstrating good selectivity for H₂S. Cellular imaging studies revealed that RM can visualize both endogenous and exogenous H₂S, offering a promising approach for monitoring SNP metabolism in biological systems.